Session key recovery system and method

• US 6,246,771 B1
• Filed: 11/26/1997
• Issued: 06/12/2001
• Est. Priority Date: 11/26/1997
• Status: Expired due to Term

• Current Assignee: SSL Services LLC
• Original Assignee: V-ONE Corp. (AEP Networks Ltd.)
• Inventors: Stanton, Leroy K., Wright, Steven R., Brook, Christopher T., Loane, Russell F.
• Primary Examiner(s): Swann, Tod
• Assistant Examiner(s): MEISLAHN, DOUGLAS J
• Application Number:
  US08/980,064
• Time in Patent Office: 1,294 Days
• Field of Search: 380/48, 380/286
• US Class Current: 380/286
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage
• CPC Class Codes: H04L 9/3234 involving additional secure or trusted devices, e.g. TPM, smartcard, USB or software token network architectures or network communication protocols for supporting authentication of entities using an additional device in a packet data network H04L63/0853

Abstract

A system and method for providing access to an encrypted communication involves recording the session during which the communication is encrypted, replaying the session to recover data used to recover a session key, accessing a server to retrieve secret information also used to generate the session key, and recreating the session key using the recovered data and secret information. The system and method includes provision for authenticating parties to the key recovery, protecting communications required to retrieve the secret key, and establishing a record of the key recovery to serve as an audit trail.

Claims

1. A key recovery system by which a key recovery agent recovers a session key used to encrypt a message, comprising:

means for the key recovery agent to replay a recorded communication between the sender of the message and an authentication server, said session key having been generated with assistance of said authentication server during said communication;

means for the key recovery agent to request the authentication server to assist in recovering the session key for use by the key recovery agent to decrypt said message, said authentication server thereupon recovering the session key from said recorded communication by recreating a process by which the session key was originally generated utilizing secret information accessible only by the authentication server;

means for the authentication server to authenticate said request by the key recovery agent to assist in recovering the session key; and

means for transmitting said session key from the authentication server to the key recovery agent in order to decrypt said message.

2. A key recovery system as claimed in claim 1, wherein said authentication server is an authentication server on a client/server network, and said secret information is stored in a database accessible only by the authentication server.

3. A key recovery system as claimed in claim 2, wherein said means for the key recovery agent to replay said recording of the session and request the authentication server to assist in recovering the session key include an applications program on a client computer connected via said client/server network to said authentication server.

4. A key recovery system as claimed in claim 3, wherein said client computer is a laptop or notebook computer.

5. A key recovery system as claimed in claim 3, wherein said means for the authentication server to authenticate said request includes means on said authentication server for cooperating with a token reader connected to said client computer to authenticate a token containing authenticating information unique to the key recovery agent in order to verify the identity of said key recovery agent.

6. A key recovery system as claimed in claim 5, wherein said token is contained on a smartcard.

7. A key recovery system as claimed in claim 6, wherein communications with said server are initially established by cooperation between said authentication server and a second customer smartcard containing authenticating information unique to the key recovery system.

8. A key recovery system as claimed in claim 6, wherein said smartcard has stored thereon an authentication certificate signed by a certification authority.

9. A key recovery system as claimed in claim 1, wherein said recorded communication includes data that has been encrypted by a public key of the party to the communication, wherein said secret information is a private key of the authentication server that can be used to decrypt said data, and wherein said authentication server includes means for decrypting said data by means of said private key.

10. A key recovery system as claimed in claim 1, wherein said recording includes first and second numbers unique to the session, and wherein said secret information is a secret key used to encrypt a combination of said first and second numbers in order to generate said session key.

11. A key recovery system as claimed in claim 1, further comprising means for transmitting information concerning a key recovery to a security officer of a customer of said encryption software in order to establish an audit trail and meet archiving requirements.

23. A key recovery system as claimed in claim 1, wherein said communication includes a ticket generated using a public/private cryptosystem-based key exchange procedure, and further comprising means for encrypting ticket information obtained from a recorded session protocol using a private key of a key recovery application'"'"'s private key, and means for sending the encrypted ticket information to the authentication server for recovery, and wherein the means for transmitting said session key from the authentication server to the key recovery agent in order to enable the recovery agent to decrypt said message includes means for encrypting a recovered session key in a public key of a user of the key recovery agent, and means for returning the recovered session key to the key recovery system.

25. A key recovery system as claimed in claim 1, wherein said authentication server is arranged to authenticate said key recovery agent based on a first token carried by and containing information unique to the key recovery agent, and to authenticate a computer used by the key recovery agent based on a second token associated with the computer and containing information unique to the key recovery system.

26. A key recovery system as claimed in claim 25, wherein said second token is contained in smartcards common to multiple key recovery agents.

27. A key recovery system as claimed in claim 25, further comprising an additional smartcard used by a chief security officer to establish communications with the authentication server in order to update secret keys used in authenticating said first and second tokens.

28. A key recovery system as claimed in claim 1, wherein said means for transmitting said session key from the authentication server to the key recovery agent includes means for encrypting the transmitted session key by a public key of the key recovery agent, a public key associated with a computer used to establish communications with the authentication server, and a private key of the authentication server, whereby the session key can only be recovered by a key recovery agent having a first token containing a private key corresponding to the public key of the key recovery agent and a second token containing a private key corresponding to the public key associated with the computer, and whereby encryption by the private key of the authentication server authenticates the authentication server.

12. A key recovery method in which a key recovery agent recovers a session key used to encrypt a message, comprising the steps of:

replaying, at the key recovery agent, a recorded communication between a sender of the message and an authentication server, said session key having been generated with assistance of the authentication server during said communication;

requesting, by the key recovery agents the authentication server to assist in recovering the session key, said authentication server thereupon recovering the session key from said recorded communication by re-creating a processing by which said session key was originally generated utilizing secret information accessible only by the authentication server;

authenticating, at the authentication server, said request by the key recovery agent to assist in recovering the session key; and

transmitting said session key from the authentication server to the key recovery agent in order to decrypt said message.

13. A key recovery method as claimed in claim 12, wherein said authentication server is an authentication server on a client/server network, and wherein said step of recovering the session key comprises the step or retrieving said secret information from a database accessible only by the authentication server.

14. A key recovery method as claimed in claim 13, wherein the steps of replaying, at the key recovery agents said recording of the session and requesting, by the authentication server, to assist in recovering the session key based on the recovered data include the step of running an applications program on a client computer connected via said client/server network to said authentication server.

15. A key recovery method as claimed in claim 14, wherein said step of running an applications program on a client computer includes the step of running the applications program on a laptop or notebook computer.

16. A key recovery method as claimed in claim 14, wherein said step of authenticating, at the authentication server, said request includes the step of authenticating, in cooperation with a token reader connected to said client computer, a token containing authenticating information unique to the key recovery agent in order to verify the identity of said key recovery agent.

17. A key recovery method as claimed in claim 16, wherein said step of authenticating said token includes the step of retrieving said token from a smartcard.

18. A key recovery method as claimed in claim 17, wherein communications with said server are initially established by cooperation between said authentication server and a second customer smartcard shared by multiple key recovery agents.

19. A key recovery method as claimed in claim 17, wherein said said step of retrieving said token from a smartcard includes the step of retrieving an authentication certificate signed by a certification authority.

20. A key recovery method as claimed in claim 12, wherein said recorded communication includes a recorded ticket containing said session key and said secret information is a private key of the authentication server, and wherein said step of recovering the session key includes the step of decrypting, by said authentication server, said recorded ticket upon accessing a database containing said private key.

21. A key recovery method as claimed in claim 12, wherein said step of replaying said recording includes the step of recovering first and second numbers unique to the session, said secret information including a secret key used to encrypt a combination of said first and second numbers in order to generate said session key.

22. A key recovery method as claimed in claim 12, further comprising the step of transmitting information concerning a key recovery to a security officer of a customer of said encryption software in order to establish an audit trail and meet archiving requirements.

24. A key recovery method as claimed in claim 12, wherein said recording includes a ticket generated using a public/private cryptosystem-based key exchange procedure, and further comprising the steps of encrypting ticket information obtained from a recorded session protocol using a private key of a key recovery application'"'"'s private key, and sending the encrypted ticket information to the server for recovery, and wherein the step of transmitting the session key to the recovery agent includes the steps of encrypting a recovered session key in a public key of a user of the key recovery agent, and returning the recovered session key to the key recovery agent.

29. A key recovery method as claimed in claim 12, wherein said step of authenticating, at said authentication server, said request by said key recovery agent includes the steps of authenticating said key recovery agent based on a first token carried by and containing information unique to the key recovery agent, and authenticating a computer used by the key recovery agent based on a second token associated with the computer and containing information unique to the key recovery system.

30. A key recovery method as claimed in claim 29, wherein step of authenticating a computer used by the key recovery agent includes the step of authenticating said computer includes the step of retrieving said second token from a smartcard common to multiple key recovery agents.

31. A key recovery method as claimed in claim 12, wherein said step of transmitting said session key from the authentication server to the key recovery agent includes the steps of encrypting the transmitted session key by a public key of the key recovery agent, a public key associated with a computer used to establish communications with the authentication server, and a private key of the authentication server, whereby the session key can only be recovered by a key recovery agent having a first token containing a private key corresponding to the public key of the key recovery agent and a second token containing a private key corresponding to the public key associated with the computer, and whereby encryption by the private key of the authentication server authenticates the authentication server.